Dry cleaning is a major industry throughout the world. In the United States alone, there are more than forty thousand dry cleaners (many of these have multiple locations). The dry cleaning industry is an essential industry in the present economy. Many articles of clothing (and other items) must be dry cleaned in order to remain clean by removal of body fats and oils, and presentable by preventing shrinking and discoloring.
The most widely used dry cleaning solvent until now has been perchloroethylene (PERC). There are numerous disadvantages to PERC including inherent toxicity and odor.
Another problem in this field is that different fabrics require different handling in the presently used systems in order to prevent damage to the fabrics during the dry cleaning process.
Prior art dry cleaning processes include the use of various solvents with appropriate machinery to accomplish the cleaning. As mentioned earlier, the solvent most widely used has been PERC. PERC has the advantage of being an excellent cleaning solvent, but the disadvantage of being a major health and environmental hazard, i.e., it has been linked to numerous forms of cancer and it is very destructive to ground water and aquatic life. In some areas PERC is prohibited due to these disadvantages. Additionally, in the past, other solvents such as petroleum-based solvents and glycol ethers and esters have been tried and used. These various solvents have been used with mixed cleaning results and problematic fabric/textile compatibility as compared to the results obtained with PERC.
The dry cleaning industry has long depended on petroleum-based solvents and the well-known chlorinated hydrocarbons, perchlorethylene and trichlorethylene, for use in the cleaning of fabrics and articles of clothing. Since the 1940's, PERC was praised as being a synthetic compound that is non-flammable and has great degreasing and cleaning qualities ideal for the dry cleaning industry. Beginning in the 1970's, PERC was found to cause liver cancer in animals. This was an alarming discovery, as dry cleaning waste was placed in landfills and dumpsters at that time, from which it leached into soil and ground water.
Environmental Protection Agency regulations gradually were tightened, culminating in a law that took effect in 1996 that required all dry cleaners to have "dry to dry" cycles, meaning that fabrics and articles of clothing go into the machine dry and come out dry. This required "closed loop" systems that can recapture almost all PERC, liquid or vapor. The process of "cycle" involves placing fabrics or articles of clothing into a specially designed washing machine that can hold 15 to 150 pounds of fabrics or articles of clothing that are visible through a circular window. Prior to being placed into the machine, the fabrics or articles of clothing are checked and treated by local hand spotting for stains. If the fabric is unusual or known to be troublesome, the label is checked to verify that the manufacturer has deemed the item safe for dry cleaning. If not, the stain may be permanent. As an example, a sugar stain may not be seen, but once it is run through the dry cleaning process, it oxidizes and turns brown. If the stain is grease related, water won't help, but PERC will as it solubilizes grease. In fact, the principle reason for dry cleaning certain clothes (which should not be washed in a regular washing machine) is to remove the build up of body oils (known as fatty acids) because they too oxidize and produce rancid nasty smells.
The grease which builds up in the solvent is removed by filter and by distilling the PERC. In other words, the dirty PERC is boiled and vapors are condensed back to a clean liquid. A small amount of detergent, typically 1 to 1.5% by volume of the total mixture, is typically mixed with PERC to help solubilize stains and/or stain residues from pre-spotting.
Before clothes are removed from the machine, the washer becomes a dryer. Hot air is blown through the compartment but, instead of being vented outside, the air stream goes through a condenser that liquefies the PERC vapors and returns them for reuse. After the washing and drying, clothes are steamed and ironed.
The dry cleaning process removes most of the PERC from the clothes, however, a small amount does remain. Different fibers of clothes retain more solvent than others. For example, natural fibers such as cottons, wools and thicker articles such as sleeping bags, down coats and shoulder pads tend to retain more solvent than the lighter articles or synthetic fibers.
Another major problem associated with dry cleaning clothes is the color fastness of the dyes used. PERC is a very aggressive solvent and quite often the dyes used by manufacturers are fugitive within PERC or other dry cleaning solvents. At times the fabric may be labeled dry clean only but the prints or surface dyes are fugitive in solvents leaving the article non-serviceable. When an article is cleaned and has a fugitive dye the article suffers and the other articles will experience redeposit of dye on their surface.
Another problem associated with the dry cleaning of fabrics is the redeposition of water-soluble soils that have been loosened from one fabric or article of clothing, and redeposited onto the same or another fabric or article of clothing being cleaned. Volatile silicone solvents alone, are extremely effective in dissolving fats, oils and other organic soils from garments and keeping them in suspension, but cannot hold water-soluble soils in suspension without the aid of a proper detergent.
The same problems exist for PERC and the hydrocarbons based solvents. Special detergents have been developed to solve the problems of suspension of water-soluble soils in these organic solvents and of the redeposition of these soils from them. Detergents developed for use with PERC are not compatible with volatile silicone solvents.
The only use of a cyclic siloxane composition for cleaning purposes is disclosed in U.S. Pat. No. 4,685,930 to Kasprzak. However, the disclosure therein is for spot cleaning applications only. There is no disclosure of immersing articles into the cyclic siloxane nor is there any suggestion of using the cyclic siloxane in a dry cleaning machine. Moreover, there is no suggestion of subjecting such articles to immersion in cyclic siloxane agitating, spinning, partial vacuum and heating in a continuous process to dry clean articles in a bulk process for removing fats, oils, grease and other soils from a large number of textile articles.